It is known that gliding motion of microtubules or actin filaments can be observed along a microscopic channel patterned in a glass or plastic substrate, in which channel motor proteins such as kinesins or myosins are adsorbed. Such gliding motion occurs due to mutual interaction between the motor proteins adsorbed in the channel and the microtubules or the actin filaments. The microscopic channel can be formed using electron beam lithography or irradiation of ultraviolet rays. See, for example, Non-Patent Publication 1 listed below. It is also known that by biotinylating the surfaces of the gliding microtubules and by causing biotin-avidin bindings between the biotinylated microtubules and targeted cargo molecules (such as streptavidin coated microbeads), the targeted cargo molecules can be loaded on and transported by the gliding microtubules. See, for example, Non-Patent Publication 2 listed below.
Because it is well-known that biotin-avidin binding has remarkable strong affinity among biological bindings, it is inherently difficult to unload the cargo molecules from the gliding microtubules once the cargo molecules are loaded on the microtubules.
Meanwhile, a system concept for loading and unloading of targeted cargo molecules (guest molecules of cyclodextrins) on and from gliding microtubules in a reversible fashion is proposed. See, for example, Non-Patent Publication 3 listed below. Such a reversible loading/unloading operation is realized by biotinylating cyclodextrin that is able to include and release a guest molecule in a controlled manner and by conjugating the biotinylated cyclodextrin with a biotinylated microtubule via streptavidin. It is difficult, however, to operate this system autonomously without external control because some external stimulation (for example, irradiation of ultraviolet rays) has to be given to achieve controlled release of the guest molecule from cyclodextrin. This drawback causes further problems in that system control becomes complicated and the system scale becomes huge as a whole due to an external control system.
[Non-Patent Publication 1]
                Y. Hiratsuka, et al., “Controlling the Direction of Kinesin-driven Microtubule Movements along Microlithographic Tracks,” Biophysical Journal, vol. 81, pp. 1555-1561, September 2001.[Non-Patent Publication 2]        H. Hess, et al., “Light-controlled Molecular Shuttles Made from Motor Proteins Carrying Cargo on Engineered Surfaces,” Nano Letters, vol. 1, No. 5, pp. 235-239, 2001.[Non-Patent Publication 3]        K. Kato, et al., “Microtubule-cyclodextrin Conjugate: Functionalization of Motile Filament with Molecular Inclusion Ability,” Bioscience, Biotechnology, and Biochemistry, vol. 69, No. 3, pp. 646-648, March 2005.        